Buffet said he and Berkshire Hathaway Vice Chairman Charlie Munger don't view the names as a "collection of ticker symbols - a financial dalliance to be terminated because of downgrades by 'the Street,' expected Federal Reserve actions, possible political developments, forecasts by economists or whatever else might be the subject du jour."

Instead, they see them as "an assembly of companies that we partly own and that, on a weighted basis, are earning about 20% on the net tangible equity capital required to run their businesses" without employing excessive debt.

Buffett called those returns "remarkable" and said they are "truly mind-blowing when compared against the return that many investors have accepted on bonds over the last decade - 3% or less on 30-year U.S. Treasury bonds, for example."

Below are Berkshire's 15 largest holdings ranked from smallest to largest market value at the end of 2018 (Note, Kraft Heinz, of which Berkshire owns 325,442,152 shares, is not included, because the conglomerate is part of a control group and must account for the investment on the "equity" method. Berkshire's Kraft investment has a cost basis of $9.8 billion and market value of $14 billion.):